JavaScript Closures Explained: How Inner Functions Retain Outer Scope Access

A closure in JavaScript occurs when an inner function retains access to variables from its outer function's scope, even after that outer function has finished executing. This behavior stems from the inner function preserving a reference to the lexical environment in which it was created. Closures enable persistent state across multiple function calls, as demonstrated when a counter variable increments correctly on repeated invocations without resetting. They are also used to simulate private variables, where data inside a function remains inaccessible directly from outside but can be manipulated through specific returned functions. Common use cases for closures include state management, data encapsulation, and building functions that remember previously computed values.